Regulation of Human Sperm Motility and Hyperactivation Components by Calcium, Calmodulin, and Protein Phosphatases

Abstract

The role of Ca2+, calmodulin, and protein phosphatases on motility and hyperactivation of noncapacitated, capacitating, and detergent-permeabilized reactivated human sperm was examined. In noncapacitated sperm, W7 inhibited percent motility (%MOT), curvilinear velocity (VCL), amplitude of lateral head displacement (ALH), and percent hyperactivation (%HYP) in an extracellular Ca2+ concentration-dependent manner (p < .05). However, in capacitating sperm, inhibition of motility by W7 was independent of external Ca2+. Treatment of reactivated sperm with a synthetic calmodulin inhibitor peptide decreased VCL and ALH in a Ca(2+)-dependent manner (p < .05). Ca2+ exhibited a dramatic influence on motility within a narrow concentration range (0.7 to 1.0 microM) in reactivated sperm. A calmodulin-dependent protein phosphatase (PP2B) was identified by activity assay, immunoblotting, and dephosphorylation of endogenous phosphoproteins. The sperm enzyme, unlike bovine brain PP2B, was inhibited by 1 microM okadaic acid (OA) in the presence of Mn2+, suggesting that the sperm enzyme is unique. In reactivated sperm, inhibition of endogenous PP2B-like activity with anti-PP2B antibodies altered ALH, whereas OA altered both VCL and ALH and also inhibited a subset of Ca(2+)-dependent dephosphorylations of cAMP-dependent phosphoproteins in capacitating sperm. These results suggest (1) an important role for calmodulin and PP2B in Ca(2+)-regulated motility parameters, particularly ALH, and (2) that modulation of human sperm motility, including hyperactivation by cAMP-dependent phosphorylation, requires calmodulin-dependent as well as other protein dephosphorylations.

Moving to the beat: a review of mammalian sperm motility regulation

“…At least some of the effects of calcium on the flagellum are likely to be achieved through CaM, because inhibition of CaM decreases sperm motility (White and Aitken 1989;Ahmad et al 1995;Si and Olds-Clarke 2000). Components of the PKA pathway can restore motility to CaM-inhibited sperm if the glycolytic products pyruvate and lactate are present in the medium (our unpublished data).…”

A Method for Preparation, Storage, and Activation of Large Populations of Immotile Sea Urchin Sperm

“…Researchin several laboratories supportsthe ideathatreversibleproteinphosphorylation is associated with initiation andmodulationof sperm motility (1)(2)(3)(4)(5). Many studies aimed at examining the intracellular signaling pathways that initiate the activation of flagellar motility have relied on detergent-permeabilized sperm reactivated with exogenous 32p-ATP (2,6).…”

“…Metabolic inhibitors or extended incubations at cold temperatures prior to reactivation of motility have been used to try to reverse the effects of background motility (3,9,10). However, these methods depend on endogenous enzyme activities that may reverse the signals originally induced in the background motility (3,(11)(12)(13) In addition, the following buffers were used: motility assay buffer (MAB), contained 1 mg/ml BSA in ASW; and non-motility assay buffer (NMAB), had 1 mg/ml BSA in MSSB or SSB.…”

Casa Parameters of Mithun Semen Treated with Melatonin

“…Calcium and its channels control the transition from symmetric to asymmetric flagella waveforms (Si, 1997) as an intracellular regulator of Ca 2+ function and have been identified both in the head and flagellar parts of spermatozoa (Tash and Means, 1983) and are believed to be a major signal transducer in Ca 2+ regulating motility. Calmodulin antagonist or lack of melatonin caused a reduction in VCL and ALH and it is related with mitochondrial membrane potential and mobility & velocity of the spermatozoa (Ahmad et al, 1996). These results suggested that melatonin has enhanced the regulatory role of Ca 2+ /calmodulin pathway in sperm motility and velocity parameters including VCL and ALH in liquid storage of mithun semen.…”